Pipes and tubular conduits – Joined sections
Reexamination Certificate
2000-06-30
2001-08-28
Brinson, Patrick (Department: 3752)
Pipes and tubular conduits
Joined sections
C138S109000, C204S196060
Reexamination Certificate
active
06279617
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a corrosion-protected metal construction, e.g. a steel pipeline system, a pump structure, an outboard marine engine or, insofar, any metal construction or structure of the kind often corrosion-protected through the assignment of one or more sacrificial anodes.
To combat corrosion, corrosion-protective measures are often taken. Such a step could consist in the use of sacrificial anodes. Another measure is the use of corrosion-resistant (stainless) high-quality steel. The use of high-quality steel, such as Titan or Duplex, is, however, very expensive.
When using sacrificial anodes well known constructively and functionally in connection with metal structures, bodies, termed sacrificial anodes, are used in the form of metal pieces made from a metal which is less noble in relation to the metal to be protected, and which connects to metal structures subsea or in moist environment above water, in order to protect the metal structure against corrosion.
Sacrificial anodes are usually made from zinc, aluminium or magnesium alloys. They are consumed through anodic solution. During its corrosion-protecting action towards the metal construction, the sacrificial anode(s) is/are consumed.
SUMMARY OF THE INVENTION
According to the present invention, this utilisation of sacrificial anodes as corrosion-protecting bodies is considered as insufficient and, thus, unsatisfactory, particularly with a view to their relatively short functional time before they are consumed.
Therefore, the object of the invention has been to indicate a better utilisation of sacrificial anodes used as corrosion-protecting bodies in metal constructions, steel pipeline systems, pumps, valves, outboard engines of aluminium, etc.
According to the invention, this object is realised by means of a sacrificial anode assigned to the metal construction, etc., of the kind as defined in the claims and which, moreover, distinguishes itself through the features also defined in the claims.
Substantially, the invention consists in that sacrificial anode body or bodies, respectively, disposed in association with said metal construction, etc., for corrosion-protecting purposes, is formed as and is included in the metal construction as a functional part thereof. In a pipe system, e.g. consisting of a plurality of interconnected pipe sections, each of the sacrificial anode bodies may be formed as a pipe section included in the pipe system, insofar as the remaining pipe section of special steel (noble metal). Then, the constructions of special steel will be protected against corrosion by means of sacrificial anode bodies formed as pipe sections.
Usually, the sacrificial anode pipe sections are regularly distributed along the length of a pipeline built up through the interconnection of special (noble) steel pipe sections and sacrificial anode pipe sections, the latter, ordinarily, appearing in a substantially smaller number than the number of special steel pipe sections.
In accordance with the invention, the sacrificial anode body is a multipurpose-means, where its corrosion protecting properties towards a metal construction are utilised in a well known manner, where the metal in the original construction is more noble than the metal from which the sacrificial anode bodies is made, simultaneously as each of said bodies is included in the metal construction as a functional part (a pipe section) thereof.
In pipelines/systems built up in accordance with the invention and e.g. consisting of pipe lengths of steel of the type 316L SS (relatively cheap special steel), and in the pipeline regularly inserted pipe lengths of carbon steel as sacrificial anodes, very large savings can be achieved, the carbon steel functioning as sacrificial anode and, thus, preventing that the more noble metal, steel, corrodes.
Connecting flanges between noble steel and carbon steel (or zinc alloy) may be electrically divided with an electric resistance between said flanges. This electric resistance can be a plastic package having an appropriate electric resistance value. Such a package would be producible from a material consisting of polyester admixed carbon powder.
The pipe lengths of precious steel will be protected against pitting, spot and crevice corrosion. In addition to its corrosion-protecting effect towards the precious steel pipe lengths, the sacrificial anodes in such a pipeline/system have the obvious additional function that they are fluid conveying in the same way as the other pipe lengths. In immersed devices such as e.g. pumps which, in prior art designs and structures, are connected to a sacrificial anode in the form of a metal piece, the latter may be shaped and designed as a functional pump part, e.g. as a housing or a cover included in the remainder of the pump structure, to which it is connected.
The invention is further explained in the following in connection with a non-limiting exemplary embodiment in the form of a fluid conducting, corrosion-protected pipeline built up of interconnected pipe lengths and includable in a larger pipe system.
REFERENCES:
patent: 3616421 (1971-10-01), Mackintosh
patent: 4216070 (1980-08-01), Debost
patent: 4284488 (1981-08-01), Brittain et al.
patent: 4370211 (1983-01-01), Hybler
patent: 4692231 (1987-09-01), St. Onge
patent: 4749627 (1988-06-01), Ishikawa et al.
patent: 5362921 (1994-11-01), Birkelund et al.
patent: 5910236 (1999-06-01), Iossel et al.
patent: 1564621 (1980-04-01), None
Aker Offshore Partner AS
Andrus Sceales Starke & Sawall LLP
Brinson Patrick
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